@SauravKumar - I would have just duped it to that, but you can't dupe a question to another site. I bountied to reward what I find to be the most correct answer to that question and mention it in my answer here.
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hbdgafAug 30 '13 at 23:03

@Sparhawk - It's less correct, because it doesn't mirror the default administrative user identically. It also uses a utility not specifically for the task at hand. usermod is specifically for modify users. The fact that useradd will do it is functional, but kludgy. Like logging in as root instead of using sudoers properly.
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hbdgafAug 30 '13 at 23:06

@Sparhawk - I don't see an alias. I see "substitute your username here". If you want to talk about it, let's go to chat instead of cluttering up the comments.
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hbdgafAug 30 '13 at 23:14

I think it's just a difference of opinion, so probably not much more to say. (For the record I was making an analogy with aliases.) Can I just ask, though, did you check to see what groups the test-user is added to in the GUI method? (As per my other comments, I run Kubuntu, so cannot check the Unity method.)
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SparhawkAug 31 '13 at 0:34

@Sparhawk I did not. But if it isn't all the default groups for the original admin user, it should be reported as a bug, not validate a sub-par answer.
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hbdgafAug 31 '13 at 2:24

Not as correct as it could be. Using adduser to change a user's group membership is clunky and bad. Usermod is cleaner, and the other answer includes other groups that are default for the admin user on a default Ubuntu desktop install.
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hbdgafAug 30 '13 at 22:54

1

The adduser command will add a new user. It will not promote an existing user to administrator. !!
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NikThAug 30 '13 at 22:54

@NikTh Are you sure? I'm fairly sure I've used this before on an existing user and it worked.
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SparhawkAug 30 '13 at 22:55

@NikTh - If you run adduser on an existing user, it will modify the user. It works, but it's clunky and shows a google-paste instead of understanding several shell utilities.
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hbdgafAug 30 '13 at 22:55

@hbdgaf 1) If the question asked for admin rights, isn't that equivalent to being added to sudo by definition? The other groups seem like they are not what has been asked for. 2) That's a bit harsh accusing me of "google-paste", since you admitted you copy-pasted anyway. And your -1 is also harsh, since it clearly does work.
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SparhawkAug 30 '13 at 22:59